The present invention relates to an iris recognition camera system for mobile devices which alloys a brightness and range of lighting and a direction of irradiation to be designed as desired by being equipped with an FPCB (flexible printed circuit board) on which an IR LED (infrared light-emitting diode) light source element is attached and with an FPCB cover (guide) either side of which has a concave-convex portion to scatter light or an FPCB cover of which materials contain a substance that scatters or diffuses light or of which surface is coated with such a substance, and also relates to an iris recognition system which is designed to effectively adjust the size of a camera by installing multiple (at least four) IR LED light source elements, which are aligned around a camera, on an FPCB, to ameliorate user convenience by visually displaying that iris recognition is being performed and to minimize the size and volume of a camera by employing an elliptical mirror optimized for iris-guiding.
Authenticated certificates are being widely used in almost all fields of electronic commerce including internet shopping, online banking, mobile stock trading, Internet issuance of public documents, etc.
Such authenticated certificates are online forms of identification that are necessary to validate a person's identity so as to allow him or her to conduct convenient internet transactions, but they are vulnerable in terms of security because the certificate files and passwords may be leaked out through hacking.
Since conventional methods for identity validation have such a problem, schemes using biological information are being pursued. In this regard, biometric technology has attracted attention as user authentication technology that provides convenience and safety, being selected as one of the “10 promising technologies for the 21st century” by MIT, Gartner Group, etc.
Iris recognition is regarded as the most secure among currently implemented biometric technologies in that the probability of one human iris having the same pattern as another is approximately one in six billions, which is supported by the fact that it is currently used as identification means in many countries including US, Japan, UK and Germany.
In general, an IR (infrared) LED light source element is used for iris recognition while the radiation angle (lighting angle) of the IR LED light source element is determined to be twice the angle that corresponds to a half of the peak relative illumination.
An example of such a radiation angle is as illustrated in FIG. 7, in which the radiation angle (lighting angle) is about 125 degrees.
An iris recognition camera lens has a specific field of vision, or field of view, which is represented in a unit of angle, and an image within its angular range may be formed on a sensor.
The field of vision of a lens may have a variety of combinations depending on the distance between the lens and the iris, the resolution (or the number of pixels) of an image sensor, the performance of a device that validates an identity based on an iris image and the structure of a program to process it.
For example, when an identity is validated via an iris image obtained with the distance between a lens and an eye set to a short distance of 5 to 15 cm and by a typical signal processing device of which speed is around a few hundred MHz, it is determined that it is sufficient if an image sensor has a resolution of about 640×480 pixels.
In this case, it may be acceptable that the field of vision of the lens is about 15 degrees that corresponds to about two or three times of the size of the pupil.
The range of lighting is preferable when it is slightly wider than the field of vision of the lens while the uniformity of the brightness of lighting should guarantee the image quality to facilitate the iris image processing, or 70 to 80% at least.
Relative uniformities of brightness may be simply compared each other based on the brightness_maximum versus brightness_minimum technique among various methods that have been introduced to determine the uniformity of brightness.
In addition, to achieve effective lighting performance, it is preferred that the lighting range be somewhat wider, by 20 to 50%, than the field of vision of a lens.
When the lighting range is excessively narrow, a variety of additional means are required to achieve the uniformity of brightness in light of the radiation characteristics of an IR LED light source element. When the lighting range is excessively wide, in contrast, relatively intense lighting is required, and thus there arises the disadvantage of power consumption and the number of lighting components both increasing. Because the brightness of lighting is inversely proportional to the square of the illuminated area, four times of the amount of light is required for the same brightness when the lighting range is double.
As illustrated in FIG. 1 and FIG. 3, an IR LED light source element 20 increases in its power consumption when it is vertically installed in an FPCB 10 because the IR LED light source element 20 requires a larger amount of light since a radiation angle (light angle) has to increase so as to irradiate an adequate amount of illumination around the iris to obtain an image of the iris of an eye that is at a certain distance from the center of a camera 70.
Additionally, there arises a disadvantage in that the IR LED light source element 20 functions as a conductor that transmits external static electricity to internal mechanical devices (not shown) and the uniformity of brightness deteriorates, when used as a short-distance lighting, around the iris.
As illustrated in FIG. 2 and FIG. 5, if an LED light source element 20 is not installed in an FPCB 10, an additional support (not shown) should be mounted so as to secure the IR LED light source element 20 and determine and maintain an arbitrary value of the radiation angle, which renders the quality control extremely difficult in mass production because it is difficult to assembly such a geometry and judge a certain angle with naked eye.
Additionally, there arises another disadvantage in that an additional support (not shown) to secure an IR LED light source 20 creates unnecessary space, renders the structure unaesthetic and increases the overall size.
Furthermore, an IR LED light source element 20 installed in the way aforementioned is directly exposed to external environment, similar to that illustrated in FIG. 3, which is vulnerable to external static electricity deteriorating the uniformity of brightness around the iris of an eye.
As illustrated in FIG. 5, an FPCB cover 60 of which upper and lower surfaces are flat may improve the uniformity of brightness around the iris but still pose a problem in optimizing the radiation angle of an IR LED light source 20.
Such an IR LED light source element 20 may employ a metallic guide to dissipate heat because an IR LED light source element 20 consumes a certain amount of electric power to obtain a predetermined amount of light output, which generates heat when it operates.
In such a case, static electricity up to a few thousand volts may be introduced from the human body or air then applied to the FPCB 10 that supplies power and discharged via its internal circuit, which may incur malfunction of the circuit of the internal devices.
Therefore, a static electricity absorption element is generally used as static electricity prevention means. The use of the static electricity absorption element is, however, a factor resulting in an increase in cost. In addition, this method sometimes requires separate measures other than the static electricity absorption element, complicating the structure of a camera module to obtain an iris image and hindering the size of the camera from being minimized, and is not appropriate to be applied to a mobile device.